Search results for "causality"
showing 10 items of 258 documents
THE CAUSAL ROOTS OF INTEGRATION AND THE UNITY OF CONSCIOUSNESS
2016
A fundamental feature of consciousness is unity. The problem is whether unity is compatible both with the physical underpinnings of conscious experience and with the fabric of the physical world in general.
Free Action and Interventionist Theory of Causality
2019
Intendo discutere il rapporto tra la teoria interventista della causalità e l’azione libera. Gli approcci interventisti alla causalità definiscono la causazione sulla base dell’“intervento”. Queste teorie possono essere riduttive, se spiegano le cause in base all’intervento umano come libero intervento umano, oppure non-riduttive, se considerano cause e interventi come due concetti inter-definiti, dove gli interventi sono considerati come esplicitamente non umani. Intendo mostrare che il dilemma tra teorie interventista della causalità di tipo riduttivo e non-riduttivo può essere superato in favore degli approcci riduttivi, con riferimento a ciò che la causazione è in senso antropologico e …
Estimation of Granger causality through Artificial Neural Networks: applications to physiological systems and chaotic electronic oscillators
2021
One of the most challenging problems in the study of complex dynamical systems is to find the statistical interdependencies among the system components. Granger causality (GC) represents one of the most employed approaches, based on modeling the system dynamics with a linear vector autoregressive (VAR) model and on evaluating the information flow between two processes in terms of prediction error variances. In its most advanced setting, GC analysis is performed through a state-space (SS) representation of the VAR model that allows to compute both conditional and unconditional forms of GC by solving only one regression problem. While this problem is typically solved through Ordinary Least Sq…
GW170817, General Relativistic Magnetohydrodynamic Simulations, and the Neutron Star Maximum Mass
2017
Recent numerical simulations in general relativistic magnetohydrodynamics (GRMHD) provide useful constraints for the interpretation of the GW170817 discovery. Combining the observed data with these simulations leads to a bound on the maximum mass of a cold, spherical neutron star (the TOV limit): ${M_{\rm max}^{\rm sph}}\lesssim 2.74/\beta$, where $\beta$ is the ratio of the maximum mass of a uniformly rotating neutron star (the supramassive limit) over the maximum mass of a nonrotating star. Causality arguments allow $\beta$ to be as high as $1.27$, while most realistic candidate equations of state predict $\beta$ to be closer to $1.2$, yielding ${M_{\rm max}^{\rm sph}}$ in the range $2.16…
Predictability decomposition detects the impairment of brain-heart dynamical networks during sleep disorders and their recovery with treatment
2016
This work introduces a framework to study the network formed by the autonomic component of heart rate variability (cardiac process η ) and the amplitude of the different electroencephalographic waves (brain processes δ , θ , α , σ , β ) during sleep. The framework exploits multivariate linear models to decompose the predictability of any given target process into measures of self-, causal and interaction predictability reflecting respectively the information retained in the process and related to its physiological complexity, the information transferred from the other source processes, and the information modified during the transfer according to redundant or synergistic interaction betwee…
On Big Data: How should we make sense of them?
2020
The topic of Big Data is today extensively discussed, not only on the technical ground. This also depends on the fact that Big Data are frequently presented as allowing an epistemological paradigm shift in scientific research, which would be able to supersede the traditional hypothesis-driven method. In this piece, I critically scrutinize two key claims that are usually associated with this approach, namely, the fact that data speak for themselves, deflating the role of theories and models, and the primacy of correlation over causation. In so doing, I will also refer to a recent case history of data mining projects in the field of biomedicine, i.e. EXPOsOMICS. My intention is both to acknow…
Assessment of Granger causality by nonlinear model identification: application to short-term cardiovascular variability.
2007
A method for assessing Granger causal relationships in bivariate time series, based on nonlinear autoregressive (NAR) and nonlinear autoregressive exogenous (NARX) models is presented. The method evaluates bilateral interactions between two time series by quantifying the predictability improvement (PI) of the output time series when the dynamics associated with the input time series are included, i.e., moving from NAR to NARX prediction. The NARX model identification was performed by the optimal parameter search (OPS) algorithm, and its results were compared to the least-squares method to determine the most appropriate method to be used for experimental data. The statistical significance of…
Cellular ionic alterations with age: relation to hypertension and diabetes.
2000
BACKGROUND: Cytosolic free calcium (Cai) and magnesium (Mgi) are vital to cellular homeostasis and function. OBJECTIVE: To evaluate cellular divalent cations in normal subjects at different ages and their relationship to ion levels in essential hypertension and diabetes. DESIGN: A cross-sectional study. SETTING: A university hospital in New York. PARTICIPANTS: A total of 103 subjects (32 older, 71.1 ± 1.2 y/o, and 71 young/middle aged subjects, 51.1 ± 2.3 y/o). INTERVENTION: Oral glucose tolerance test. MEASUREMENTS: 19F and 31P NMR spectroscopy were used to measure Cai and Mgi levels in erythrocytes from normal (>65 y/o, n = 11; 65 y/o, n = 9; 65 y/o, n = 12; <65 y/o, n = 15) subjects; the…
Towards understanding the complexity of cardiovascular oscillations: Insights from information theory.
2018
Abstract Cardiovascular complexity is a feature of healthy physiological regulation, which stems from the simultaneous activity of several cardiovascular reflexes and other non-reflex physiological mechanisms. It is manifested in the rich dynamics characterizing the spontaneous heart rate and blood pressure variability (HRV and BPV). The present study faces the challenge of disclosing the origin of short-term HRV and BPV from the statistical perspective offered by information theory. To dissect the physiological mechanisms giving rise to cardiovascular complexity in different conditions, measures of predictive information, information storage, information transfer and information modificati…
Brain Activity Characterization Induced by Alcoholic Addiction: Spectral and Causality Analysis of Brain Areas Related to Control and Reinforcement o…
2014
Addiction to drugs generates modifications in the brain structure and its functions. In this work, an experimental model is described, using rats to characterize the brain activity induced by alcohol addiction. Four records were obtained using electrodes located in brain areas related to impulsivity control and reinforcement, i.e. the prelimbic (PL) and infralimbic (IL) cortex, together with the hippocampus (HPC). In the records, three main events related to the drinking action were selected: in the previous minute (T1), the first minute while drinking (T2) and the first minute after stopping drinking (T3).